what are Optical Finger print sensor?
ANS: Optical sensors use arrays of photodiode or phototransistor detectors to convert the energy in light incident on the detector into electrical charge. The sensor package usually includes a light-emitting-diode (LED) to illuminate the finger. There are two detector types used by optical sensors, charge-coupled-devices (CCD) and CMOS based optical imagers. CCD detectors are sensitive to low light levels and are capable of making excellent greyscale pictures. However, CCD fabrication is relatively expensive and neither low-light sensitivity nor greyscale imaging is required for fingerprint recognition. CMOS optical imagers are manufactured in quantity and can be made with some of the image processing steps built into the chip resulting in a lower cost.
